The electrochemical reduction of oxygen on a strontium doped lanthanum manganite (LSM) electrode has been studied by both low field and high field polarization at various partial pressures of oxygen and temperature. The reciprocal of the electrode resistance (T/R-e) was found to be 1/4 power dependent on the partial pressure of oxygen at high temperatures, and became P-O2 independent at low temperatures. Two temperature dependence regions with an activation energy of similar to 160 kJ mol(-1) in the high temperature region and similar to 120 kJ mol(-1) in the low temperature region were determined. Both the anodic and cathodic charge transfer coefficients were found to be unity at temperatures above 923 K. Based on the results for the temperature and oxygen partial pressure dependence, an electrochemical mechanism for oxygen reduction on the LSM has been proposed.